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111.
We study the dynamics of periodic arrays of micrometer-sized liquid-gas menisci formed at superhydrophobic surfaces immersed into water. By measuring the intensity of optical diffraction peaks in real time, we are able to resolve nanometer-scale oscillations of the menisci with submicrosecond time resolution. Upon driving the system with an ultrasound field at variable frequency, we observe a pronounced resonance at a few hundred kilohertz, depending on the exact geometry. By modeling the system using the unsteady Stokes equation, we find that this low resonance frequency is caused by a collective mode of the acoustically coupled oscillating menisci. 相似文献
112.
Tandiono T Ow DS Driessen L Chin CS Klaseboer E Choo AB Ohl SW Ohl CD 《Lab on a chip》2012,12(4):780-786
We report on an efficient ultrasound based technique for lysing Escherichia coli and Pichia pastoris with oscillating cavitation bubbles in an integrated microfluidic system. The system consists of a meandering microfluidic channel and four piezoelectric transducers mounted on a glass substrate, with the ultrasound exposure and gas pressure regulated by an automatic control system. Controlled lysis of bacterial and yeast cells expressing green fluorescence protein (GFP) is studied with high-speed photography and fluorescence microscopy, and quantified with real-time polymerase chain reaction (qRT-PCR) and fluorescence intensity. The effectiveness of cell lysis correlates with the duration of ultrasound exposure. Complete lysis can be achieved within one second of ultrasound exposure with a temperature increase of less than 3.3 °C. The rod-shaped E. coli bacteria are disrupted into small fragments in less than 0.4 seconds, while the more robust elliptical P. pastoris yeast cells require around 1.0 second for complete lysis. Fluorescence intensity measurements and qRT-PCR analysis show that functionality of GFP and genomic DNA for downstream analytical assays is maintained. 相似文献
113.
Heterogeneous bubble nucleation at surfaces has been notorious because of its irreproducibility. Here controlled multibubble surface cavitation is achieved by using a hydrophobic surface patterned with microcavities. The expansion of the nuclei in the microcavities is triggered by a fast lowering of the liquid pressure. The procedure allows us to control and fix the bubble distance within the bubble cluster. We observe a perfect quantitative reproducibility of the cavitation events where the inner bubbles in the two-dimensional cluster are shielded by the outer ones, reflected by their later expansion and their delayed collapse. Apart from the final bubble collapse phase (when jetting flows directed towards the cluster's center develop), the bubble dynamics can be quantitatively described by an extended Rayleigh-Plesset equation, taking pressure modification through the surrounding bubbles into account. 相似文献
114.
Sascha Reith Serhiy Demeshko Beatrice Battistella Alexander Reckziegel Christian Schneider Andreas Stoy Crispin Lichtenberg Franc Meyer Dominik Munz C. Gunnar Werncke 《Chemical science》2022,13(26):7907
Imidyl and nitrene metal species play an important role in the N-functionalisation of unreactive C–H bonds as well as the aziridination of olefines. We report on the synthesis of the trigonal imido iron complexes [Fe(NMes)L2]0,− (L = –N{Dipp}SiMe3); Dipp = 2,6-diisopropyl-phenyl; Mes = (2,4,6-trimethylphenyl) via reaction of mesityl azide (MesN3) with the linear iron precursors [FeL2]0,−. UV-vis-, EPR-, 57Fe Mössbauer spectroscopy, magnetometry, and computational methods suggest for the reduced form an electronic structure as a ferromagnetically coupled iron(ii) imidyl radical, whereas oxidation leads to mixed iron(iii) imidyl and electrophilic iron(ii) nitrene character. Reactivity studies show that both complexes are capable of H atom abstraction from C–H bonds. Further, the reduced form [Fe(NMes)L2]− reacts nucleophilically with CS2 by inserting into the imido iron bond, as well as electrophilically with CO under nitrene transfer. The neutral [Fe(NMes)L2] complex shows enhanced electrophilic behavior as evidenced by nitrene transfer to a phosphine, yet in combination with an overall reduced reactivity.A pair of trigonal imido iron complexes ([Fe(NMes)L2]0,−) in two oxidation states is reported. The anionic complex K{crypt.222}[Fe(NMes)L2] is best described as an iron(ii) imide. 相似文献
115.
Dr. Jan Lorkowski Dylan Bouetard Patrick Yorkgitis Dr. Milan Gembicky Dr. Thierry Roisnel Dr. Nicolas Vanthuyne Prof. Dr. Dominik Munz Dr. Ludovic Favereau Prof. Dr. Guy Bertrand Dr. Marc Mauduit Dr. Rodolphe Jazzar 《Angewandte Chemie (International ed. in English)》2023,62(33):e202305404
Organic circularly polarized luminescence (CPL)-active molecular emitters featuring dynamic propeller-like luminophores were prepared in one step from cyclic(alkyl)(amino) carbenes (CAACs). These molecules exhibit through-space arene-arene π-delocalization and rapid intramolecular inter-system crossing (ISC) in line with their helical character. 相似文献
116.